1. Field of the Invention
The present invention relates to a technique of controlling an air volume, at the time when the operation mode is switched to the defroster mode, in an air-conditioner for vehicle use.
2. Description of the Related Art
The official gazette of JP-A-60-4409 describes an air-conditioner for vehicle use in which a passenger selects the defroster mode by manual operation as the blowout mode for blowing out air into a vehicle passenger compartment, and then this operation of selecting the defroster mode is judged by the air-conditioner and the minimum level of an air volume blown out into the vehicle passenger compartment is increased by a predetermined value.
According to this prior art, as a volume of air blown out at the time of the defroster mode is increased, the capacity of removing a fog from the windshield can be enhanced.
However, according to this prior art, when the passenger selects the defroster mode by a manual operation, immediately after the manual operation, the minimum level of the volume of air blown out into the vehicle passenger compartment is increased. Therefore, such a phenomenon is caused that the volume of air blown out into the vehicle passenger compartment is increased before the blowout mode is completely switched to the defroster mode.
That is, an increase in the volume of air can be instantaneously conducted by an electrical control operation of increasing voltage impressed upon a fan motor. On the other hand, when the blowout mode is switched, it is necessary to conduct a mechanical operation of moving a blowout mode door, between a plurality of blowout ports, by a predetermined distance. Therefore, as compared with a period of time in which the volume of blowout air is increased, it takes a long period of time when the blowout mode door is moved between the plurality of blowout ports.
As a result, before the blowout mode is completely switched to the defroster mode, the volume of air blown out into the vehicle passenger compartment is increased. Accordingly, when the blowout mode is switched from the face mode to the defroster mode, a volume of air blown out from the face blowout port is increased before the completion of the blowout mode, and the noise of blowing air is increased.
In this case, the face blowout port is located at the closest position to the ears of the passenger, and an air passage connected to the face blowout port is designed in such a manner that the air passing resistance is the smallest among a plurality of blowout ports so that the maximum cooling performance (the cooling down performance) can be ensured. Therefore, the passenger can easily feel an increase in the sound intensity of noise caused by the increase in the volume of air blown out from the face blowout port. As a result, the passenger is made uncomfortable.